The present invention relates to propylene polymers containing
a) from 50 to 95 parts by weight of a propylene homopolymer having a melt flow index of from 0.1 to 100 g/10 min. at 230xc2x0 C. and under a weight of 2.16 kg, according to ISO standard 1133, and an isotacticity index of at least 98%,
b) from 5 to 50 parts by weight of an ethylene copolymer containing from 4 to 40% by weight of polymerized C4-C20-alk-1-ene and having a density of from 0.865 to 0.920 g/cm3 and
c) from 0 to 1.5 parts by weight of a nucleating agent, the sum of the parts by weight of the propylene homopolymer a) and of the ethylene copolymer b) always being 100 parts by weight.
The present invention furthermore relates to a process for the preparation of these polymers and to their use as films, fibers and moldings.
The preparation of propylene homopolymers by Ziegler-Natta polymerization has long been known. The catalyst components used contain, inter alia, compounds of polyvalent titanium, aluminum halides and/or alkyls, as well as electron donor compounds, silanes, esters, ketones or lactones generally being used (DE-A 42 16 548, DE-A 44 19 438, EP-A 171 200, EP-A 530 599, U.S. Pat. No. 4,857,613).
In this process, propylene homopolymers having very different properties can be obtained, for example having substantially different rigidity, impact strength or flowability. Some applications in which propylene polymers are preferably used require in particular propylene polymers which, in addition to a high impact strength, also have, for optical reasons, a substantially reduced tendency to white fracture and high rigidity.
In addition to the preparation of propylene polymers by means of Ziegler-Natta catalysts, it is has also been possible for some years to prepare polymers of propylene and of ethylene with the use of metallocene catalysts having cyclic ligands (EP-A 519 237, EP-A 692 499).
DE-A 4407327 describes propylene polymers which consist of a propylene homopolymer and a nucleating agent and are distinguished, inter alia, by high rigidity and flowability. For certain applications of propylene polymers, however, even higher rigidity and improved white fracture behavior are of interest.
EP-A 593 221 discloses mixtures of propylene polymers and ethylene copolymers with polymerized C4-C18-alk-1-enes, whose density is less than or equal to 0.913 g/cm3. The blends mentioned therein have good impact strength and rigidity, but the manner in which the white fracture behavior of such products can be improved is not described.
Furthermore, WO-A 94/06859 claims blends of thermoplastic polymers and linear ethylene copolymers with polymerized C3-C20-alk-1-enes, which have, inter alia, high transparency and good impact strength at low temperatures. However, WO-A 94/06859 does not indicate how the white fracture behavior of such blends can be improved and at the same time their rigidity increased.
It is an object of the present invention to remedy the disadvantages described and to provide an improved propylene polymer which is distinguished by an advantageous property profile in terms of good impact strength, flowability and processability and moreover has high rigidity and very little tendency to white fracture.
We have found that this object is achieved by novel propylene polymers containing
a) from 50 to 95 parts by weight of a propylene homopolymer having a melt flow index of from 0.1 to 100 g/10 min. at 230xc2x0 C. and under a weight of 2.16 kg, according to ISO standard 1133, and an isotacticity index of at least 98%,
b) from 5 to 50 parts by weight of an ethylene copolymer containing from 4 to 40% by weight of polymerized C4-C20-alk-1-ene and having a density of from 0.865 to 0.920 g/cm3 and
c) from 0 to 1.5 parts by weight of a nucleating agent, the sum of the parts by weight of the propylene homopolymer a) and of the ethylene copolymer b) always being 100 parts by weight.
Propylene polymers which contain
a) from 60 to 90, in particular from 75 to 90, parts by weight of the propylene homopolymer a),
b) from 10 to 40, in particular from 10 to 25, parts by weight of the ethylene copolymer b) and
c) from 0 to 1.5, in particular from 0.05 to 1.5, parts by weight of the nucleating agent c) are particularly preferred.
The sum of the parts by weight of the propylene homopolymer and of the ethylene copolymer b) is always 100 parts by weight.
A preferably used propylene homopolymer a) is one which has a melt flow index of from 0.2 to 50 g/10 min at 230xc2x0 C. and under a weight of 2.16 kg, according to ISO standard 1133. The melt flow index corresponds to the amount of polymer in grams which is forced, at 230xc2x0 C. and under a weight of 2.16 kg, out of the test apparatus standardized according to ISO standard 1133.
The novel propylene polymer contains in particular a propylene homopolymer a) whose isotacticity index is at least 98.0%, preferably from 98.0% to 99.5%. The isotacticity index is to be understood as meaning that proportion of polymer which is insoluble in xylene according to ISO standard 6427 b). The isotacticity index is a measure of the stereospecificity of the propylene homopolymer.
The process leading to these propylene homopolymers a) can be carried out either batchwise or, preferably, continuously in the conventional reactors used for the polymerization of propylene. Suitable reactors include continuously operated stirred kettles. The reactors contain a fixed bed of finely divided polymer, which is usually kept in motion by stirring.
The process can be carried out with the Ziegler-Natta catalysts conventionally used in polymerization technology. In addition to a titanium-containing solid component, these also contain, inter alia, a cocatalyst. A suitable cocatalyst is an aluminum compound. In addition to this aluminum compound, an electron donor compound is also used as a further component of the cocatalyst.
For the preparation of the titanium-containing solid component, the titanium compounds used are in general halides or alcoholates of trivalent or tetravalent titanium, the chlorides of titanium, in particular titanium tetrachloride, being preferred. The titanium-containing solid component advantageously contains a finely divided carrier, for which silicas and aluminas as well as aluminum silicates of the empirical formula SiO2.aAl2O3, where a is from 0.001 to 2, in particular from 0.01 to 0.5, have proven useful.
The preferably used carriers have a particle diameter of from 0.1 to 1000 xcexcm, in particular from 10 to 300 xcexcmm, a pore volume of from 0.1 to 10, in particular from 1.0 to 5.0, cm3/g and a specific surface area of from 10 to 1000, in particular from 100 to 500, m2/g.
In particular, a finely divided inorganic oxide which has a pH of from 1 to 6, a mean particle diameter of from 5 to 200 xcexcm, in particular from 20 to 70 xcexcm and a mean primary particle diameter of from 1 to 20 xcexcm, in particular from 1 to 5 xcexcm, may be used as the finely divided carrier for the titanium-containing solid component. The primary particles are porous, granular oxide particles which are obtained from a corresponding hydrogel by milling, if necessary after sieving has been carried out. The hydrogel is produced in the acidic range, ie. at a pH of from 1 to 6, or is aftertreated with appropriately acidic wash solutions and purified.
Inter alia, the finely divided inorganic oxide also has cavities or channels having an average diameter of from 0.1 to 20 xcexcm, in particular from 1 to 15 xcexcm, whose macroscopic volume fraction is from 5 to 30%, in particular from 10 to 30%, based on the total particle. The finely divided inorganic oxide furthermore has in particular a pore volume of from 0.1 to 10, preferably from 1.0 to 4.0, cm3/g and a specific surface area of from 10 to 1000, preferably from 100 to 500, m2/g. The pH, ie. the negative decadic logarithm of the proton concentrations of the inorganic oxide is from 1 to 6, in particular from 2 to 5.
Preferred inorganic oxides are in particular oxides of silicon, of aluminum, of titanium or of one of the metals of main group I or II of the Periodic Table. In addition to alumina or magnesium oxide or a sheet silicate, another very preferably used oxide is silica gel (SiO2), which can be obtained, in particular, by spray-drying. It is also possible to use cogels, ie. mixtures of two different inorganic oxides. However, such finely divided inorganic oxides are also commercially available.
Inter alia, compounds of magnesium are also used in the preparation of the titanium-containing solid component. Particularly suitable compounds of this type are magnesium halides, alkylmagnesiums and arylmagnesiums, as well as alkoxymagnesium and aryloxymagnesium compounds, magnesium chloride, magnesium bromide and di(C1-C10-alkyl)magnesium compounds being preferably used. In addition, the titanium-containing solid component may contain halogen, preferably chlorine or bromine.
The titanium-containing solid component furthermore contains electron donor compounds, for example mono- or polyfunctional carboxylic acids, carboxylic anhydrides and carboxylic esters, ketones, ethers, alcohols, lactones and organophosphorus and organosilicon compounds. Preferably used electron donor compounds within the titanium-containing solid component are phthalic acid derivatives of the general formula I 
where X and Y are each chlorine or a C1-C10-alkoxy or together are oxygen. Particularly preferred electron donor compounds are phthalic esters, where X and Y are each C1-C8-alkoxy, for example methoxy, ethoxy, propoxy or butoxy.
Further preferred electron donor compounds within the titanium-containing solid component include diesters of 3- or 4-membered, unsubstituted or substituted cycloalkane-1,2-dicarboxylic acids and monoesters of unsubstituted or substituted benzophenone-2-carboxylic acids. Hydroxy compounds used in the case of these esters are the alcohols conventionally employed in esterification reactions, including C1-C15-alkanols, C5-C7-cycloalkanols, which in turn may carry C1-C10-alkyl groups, and phenols, naphthols and the C1-C10-alkyl derivatives of these compounds.
The titanium-containing solid components can be prepared by methods known per se. Examples of these are described, inter alia, in EP-A 171 200, GB-A 2 111 066, U.S. Pat. Nos. 4,857,613 and 5,288,824.
In the preparation of the titanium-containing solid component, the following three-stage process is preferably used.
In the first stage, a solution of the magnesium-containing compound in a liquid alkane is first added to a finely divided carrier, preferably silica or SiO2.aAl2O3, where a is a number from 0.001 to 2, in particular from 0.01 to 0.5, after which this mixture is stirred for from 0.5 to 5 hours at from 10 to 120xc2x0 C. Preferably, from 0.1 to 1 mol of the magnesium compound is used per mole of the carrier. A halogen or a hydrogen halide, in particular chlorine or hydrogen chloride, is then added, with continuous stirring, in an at least two-fold, preferably at least five-fold, molar excess, based on the magnesium-containing component. After from about 30 to 120 minutes, the solid is isolated from the liquid phase.
In the second stage, the product obtained in this manner is introduced into a liquid alkane, and a C1-C8-alkanol, in particular ethanol, a halide or an alcoholate of trivalent or tetravalent titanium, in particular titanium tetrachloride, and an electron donor compound, in particular a phthalic acid derivative of the general formula I, are then added. From 1 to 5, in particular from 2 to 4, mol of alkanol, from 2 to 20, in particular from 4 to 10, mol of trivalent or tetravalent titanium and from 0.01 to 1, in particular from 0.1 to 1.0, mol of the electron donor compound are used per mole of magnesium in a solid obtained in the first stage. This mixture is stirred for at least one hour at from 10 to 150xc2x0 C. and the solid substance thus obtained is then filtered off and is washed with a liquid alkane, preferably with hexane or heptane.
In the third stage, the solid obtained in the second stage is extracted for some hours at from 100 to 150xc2x0 C. with excess titanium tetrachloride or with an excess of a solution of titanium tetrachloride in an inert solvent, preferably an alkylbenzene, the solvent containing at least 5% by weight of titanium tetrachloride. The product is then washed with a liquid alkane until the titanium tetrachloride content of the wash liquid is less than 2% by weight.
The titanium-containing solid component obtainable in this manner is used with a cocatalyst as the Ziegler-Natta catalyst system. A suitable cocatalyst is an aluminum compound.
Suitable aluminum compounds in addition to trialkylaluminum are also those compounds in which an alkyl group is replaced by an alkoxy group or by a halogen atom, for example by chlorine or bromine.
Preferably used trialkylaluminum compounds are those whose alkyl groups are each of 1 to 8 carbon atoms, for example trimethyl-, triethyl- or methyldiethylaluminum.
Further cocatalysts which are preferably used in addition to the aluminum compound are electron donor compounds, for example mono- or polyfunctional carboxylic acids, carboxylic anhydrides and carboxylic esters, ketones, ethers, alcohols, lactones and organophosphorus and organosilicon compounds. Particularly suitable electron donor compounds are organosilicon compounds of the general formula II
Rxe2x80x2nSi(ORxe2x80x3)4xe2x88x92nxe2x80x83xe2x80x83II
where the radicals Rxe2x80x2 are identical or different and are each C1-C20-alkyl, 5- to 7-membered cycloalkyl, which in turn may carry a C1-C10-alkyl, or a C6-C20-arylalkyl, the radicals Rxe2x80x3 are identical or different and are each C1-C20-alkyl and n is 1, 2 or 3. Particularly preferred compounds are those in which Rxe2x80x2 is C1-C8-alkyl or 5- to 7-membered cycloalkyl, Rxe2x80x3 is C1-C4-alkyl and n is 1 or 2.
Among these compounds, dimethoxydiisopropylsilane, dimethoxyisobutylisopropylsilane, dimethoxydiisobutylsilane, dimethoxydicyclopentylsilane, dimethoxy-sec-butylisopropylsilane, diethoxydicyclopentylsilane, diethoxy-sec-butylisopropylsilane and diethoxyisobutylisopropylsilane are noteworthy.
Preferably used catalyst systems are those in which the atomic ratio of aluminum from the aluminum compound to titanium from the titanium-containing solid component is from 10:1 to 800:1, in particular from 20:1 to 200:1, and the molar ratio of the aluminum compound to the electron donor compound used as the cocatalyst is from 1:1 to 100:1, in particular from 2:1 to 20:1. The catalyst components may be introduced into the polymerization system individually in any desired order or as a mixture of components.
The polymerization for the preparation of the propylene homopolymers a) is usually carried out at from 20 to 40 bar and from 60 to 90xc2x0 C. and with an average residence time of the reaction mixture of from 0.5 to 5 hours. Pressures of from 25 to 35 bar, temperatures of from 65 to 85xc2x0 C. and average residence times of from 1.0 to 4 hours are preferred. The polymerization conditions are usually chosen so that from 0.05 to 2, preferably from 0.1 to 1.5, kg of the propylene homopolymer a) are formed per mmol of the aluminum component.
The molecular weight of the polymers obtainable in this way can be controlled in the usual manner by adding regulators, in particular hydrogen. C2-C6-Alk-1-enes, for example ethylene or but-1-ene, may also be used as regulators. In this case, the propylene homopolymer a) may also contain up to 0.1% by weight of other C2-C6-alk-1-enes.
A particularly used ethylene copolymer b) is a copolymer which contains from 4 to 40, preferably from 7 to 30, % by weight of polymerized C4-C20-alk-1-enes. Preferred comonomers in the ethylene copolymer b) are C4-C12-alk-1-enes, but-1-ene, pent-1-ene, 4-methylpent-1-ene, hex-1-ene, hept-1-ene or oct-1-ene or mixtures of these C4-C12-comonomers being preferably used. Particularly suitable comonomers are but-1-ene, hex-1-ene and oct-1-ene.
The ethylene copolymers b) present in the novel ethylene copolymers b) have a density of from 0.865 to 0.920, in particular from 0.868 to 0.910, g/cm3. The melt flow index at 230xc2x0 C. and under a weight of 2.16 kg, according to ISO standard 1133, is from 0.1 to 100, in particular from 1 to 30, g/10 min.
The ethylene copolymers b) contained in the novel propylene polymers are usually prepared by appropriate polymerization using metal-containing catalysts, for example using catalysts based on a metallocene complex or with the aid of titanium- and aluminum-containing Ziegler catalysts, or by means of Phillips catalysts based on chromium-containing compounds. The polymerization reaction can be carried out using the reactors usually employed in industry, either in the gas phase, in solution, in liquid monomers or in a suspension. Polymerization may be effected continuously, semicontinuously or batchwise.
The ethylene copolymers b) are preferably prepared by polymerization of ethylene and the corresponding C4-C20-alk-1-enes with the aid of catalyst systems which contain
A) if required, an inorganic carrier,
B) at least one metallocene complex,
C) at least one compound forming metallocenium ions and
D) if required, at least one organic metal compound of an alkali metal or alkaline earth metal or of a metal of main group III of the Periodic Table.
The polymerization with the aid of such metallocene-containing catalyst systems, which leads to the ethylene copolymers b), is carried out in particular at from xe2x88x9250 to 300xc2x0 C., preferably from 0 to 150xc2x0 C., and at from 0.5 to 3000, preferably from 1 to 80, bar. In this process, the residence times of the respective reaction mixtures should be set at from 0.5 to 5, in particular from 0.7 to 3.5, hours. Inter alia, antistatic agents and molecular weight regulators, for example hydrogen, may also be present during the polymerization.
The polymerization can be carried out in solution, in suspension, in liquid monomers or in the gas phase. The polymerization is preferably carried out in suspension or in the gas phase.
The polymerization process for the preparation of the copolymers b) may be carried out either continuously or batchwise. Suitable reactors include continuously operated stirred kettles, and, if necessary, a plurality of stirred kettles connected in series may also be used (reactor cascade).
Such metallocene-containing catalyst systems contain, if required, an inorganic carrier as component A). In particular, an inorganic oxide which has a pH of from 1 to 6, determined according to S. R. Morrison, xe2x80x9cThe Chemical Physics of Surfacesxe2x80x9d, Plenum Press, New York [1977], page 130 et seq., and cavities and channels whose macroscopic volume fraction is from 5 to 30% of the total particle is used as the inorganic carrier. Particularly preferably used inorganic oxides are those whose pH, ie. whose negative decadic logarithm of the proton concentration, is from 2 to 5.5, in particular from 2 to 5. In particular, those inorganic oxides which have cavities and channels whose macroscopic volume fraction is from 8 to 30%, preferably from 10 to 30%, and particularly preferably from 15 is 25%, of the total particle are furthermore used as inorganic carriers.
Further preferably used inorganic carriers include those inorganic oxides which have a mean particle diameter of from 5 to 200 xcexcm, in particular from 20 to 90 xcexcm, and a mean primary particle diameter of from 1 to 20 xcexcm, in particular from 1 to 5 xcexcm. The primary particles are porous, granular particles and have pores with a diameter of, in particular, from 1 to 1000 xc3x85. Furthermore, such inorganic oxides have, inter alia, cavities and channels having an average diameter of from 0.1 to 20 xcexcm, in particular from 1 to 15 xcexcm. The inorganic oxides furthermore have, in particular, a pore volume of from 0.1 to 10, preferably from 1.0 to 5.0, cm3/g and a specific surface area of from 10 to 1000, preferably from 100 to 500, m2/g.
Owing to the cavities and channels present in the finely divided inorganic oxides, there is a substantially improved distribution of catalyst active components in the carrier. The acidic centers at the surface of the inorganic oxide additionally result in homogeneous loading with the catalyst components. In addition, a material containing cavities and channels throughout in this manner has an advantageous effect on the diffusion-controlled supply with monomers and cocatalysts and hence also on the polymerization kinetics.
Such a finely divided inorganic oxide is obtainable, inter alia, by spray-drying milled, appropriately sieved hydrogels, which for this purpose are converted into a slurry with water or with an aliphatic alcohol. During the spray-drying, the required pH of from 1 to 6 can also be established by the use of appropriately acidic suspensions of primary particles. However, such a finely divided inorganic oxide is also commercially available.
Preferred inorganic carriers are in particular oxides of silicon, of aluminum, of titanium or of one of the metals of main group I or II of the Periodic Table. In addition to alumina or magnesium oxide or a sheet silicate, another very preferably used inorganic oxide is silica gel (SiO2), which can be obtained, in particular, by spray-drying.
Cogels, ie. mixtures of at least two different inorganic oxides, may also be used as component A).
From 0.1 to 10000, in particular from 5 to 200, xcexcmol of the metallocene complex, ie. of component B), are preferably used per gram of carrier, ie. of component A).
The preferably used metallocene-containing catalyst system contains, as component B), at least one or more metallocene complexes. Particularly suitable metallocene complexes are those of the general formula IV 
where
M is titanium, zirconium, hafnium, vanadium, niobium or tantalum or an element of subgroup III of the Periodic Table or a lanthanoid,
X is fluorine, chlorine, bromine, iodine, hydrogen, C1-C10-alkyl, C6-C15-aryl, alkylaryl having 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical, xe2x80x94OR10 or xe2x80x94NR10R11,
n is an integer from 1 to 3 and corresponds to the valency of M minus 2,
R10 and R11 are each C1-C10-alkyl, C6-C15-aryl, alkylaryl, arylalkyl, fluoroalkyl or fluoroaryl, each having 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical,
R5 to R9 are each hydrogen, C1-C10-alkyl, 5- to 7-membered cycloalkyl, which in turn may carry C1-C10-alkyl as a substituent, C6-C15-aryl or arylalkyl, where two adjacent radicals together may form a saturated or unsaturated cyclic group of 4 to 15 carbon atoms, or Si(R12)3,
R12 is C1-C10-alkyl, C3-C10-cycloalkyl or C6-C15-aryl,
Z is X or 
R13 to R17 are each hydrogen, C1-C10-alkyl, 5- to 7-membered cycloalkyl, which in turn may carry C1-C10-alkyl as a substituent, C6-C15-aryl or arylalkyl, where two adjacent radicals together may furthermore form a saturated or unsaturated cyclic group of 4 to 15 carbon atoms, or Si(R18)3,
R18 is C1-C10-alkyl, C6-C15-aryl or C3-C10-cycloalkyl,
or R8 and Z together form a group xe2x80x94R19xe2x80x94Axe2x80x94, 
xe2x80x83xe2x95x90BR20, xe2x95x90AlR20, xe2x80x94Gexe2x80x94, xe2x80x94Snxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x95x90SO, xe2x95x90SO2, xe2x95x90NR20, xe2x95x90CO, xe2x95x90PR20 or xe2x95x90P(O)R20,
R20, R21 and R22A are identical or different and are each hydrogen, halogen, C1-C10-alkyl, C1-C10-fluoroalkyl, C6-C10-fluoroaryl, C6-C10-aryl, C1-C10-alkoxy, C2-C10-alkenyl, C7-C40-arylalkyl, C8-C40-aryl-alkenyl or C7-C40-alkylaryl or two adjacent radicals together with the atoms linking them form a ring, and
M2 is silicon, germanium or tin, 
R23 is C1-C10-alkyl, C6-C15-aryl, C3-C10-cycloalkyl, alkylaryl or Si(R24)3, and
R24 is hydrogen or C1-C10-alkyl or is C6-C15-aryl which in turn may be substituted by C1-C4-alkyl, or is C3-C10-cycloalkyl,
or R8 and R16 together form a group xe2x80x94R1913 .
Preferred metallocene complexes of the general formula IV are 
The radicals X may be identical or different but are preferably identical.
Particularly preferred compounds of the formula IVa are those in which
M is titanium, zirconium or hafnium,
X is chlorine, C1-C4-alkyl or phenyl,
n is 2 and
R5 to R9 are each hydrogen or C1-C4-alkyl.
Preferred compounds of the formula IVb are those in which
M is titanium, zirconium or hafnium,
X is chlorine, C1-C4-alkyl or phenyl,
n is 2,
R5 to R9 are each hydrogen, C1-C4-alkyl or Si(R12)3, and
R13 to R17 are each hydrogen, C1-C4-alkyl or Si(R18)3.
Particularly suitable compounds of the formula IVb are those in which the cyclopentadienyl radicals are identical.
Examples of particularly suitable compounds include:
bis(cyclopentadienyl)zirconium dichloride,
bis(pentamethylcyclopentadienyl)zirconium dichloride,
bis(methylcyclopentadienyl)zirconium dichloride,
bis(ethylcyclopentadienyl)zirconium dichloride,
bis(n-butylcyclopentadienyl)zirconium dichloride and
bis(trimethylsilylcyclopentadienyl)zirconium dichloride
and the corresponding dimethylzirconium compounds.
Particularly suitable compounds of the formula IVc are those in which
R5 and R13 are identical and are each hydrogen or C1-C10-alkyl,
R9 and R17 are identical and are each hydrogen, methyl, ethyl, isopropyl or tert-butyl,
R7 and R15 are each C1-C4-alkyl,
R6 and R14 are each hydrogen
or two adjacent radicals R6 and R7 on the one hand and R14 and R15 on the other hand together form a cyclic group of 4 to 12 carbon atoms, 
M is titanium, zirconium or hafnium and
X is chlorine, C1-C4-alkyl or phenyl.
Examples of particularly suitable complex compounds include
dimethylsilanediylbis(cyclopentadienyl)zirconium dichloride,
dimethylsilanediylbis(indenyl)zirconium dichloride,
dimethylsilanediylbis(tetrahydroindenyl)zirconium dichloride,
ethylenebis(cyclopentadienyl)zirconium dichloride,
ethylenebis(indenyl)zirconium dichloride,
ethylenebis(tetrahydroindenyl)zirconium dichloride,
tetramethylethylene-9-fluorenylcyclopentadienylzirconium dichloride,
dimethylsilanediylbis(3-tert-butyl-5-methylcyclopentadienyl)zirconium dichloride,
dimethylsilanediylbis(3-tert-butyl-5-ethylcyclopentadienyl)zirconium dichloride,
dimethylsilanediylbis(2-methylindenyl)zirconium dichloride,
dimethylsilanediylbis(2-isopropylindenyl)zirconium dichloride,
dimethylsilanediylbis(2-tert-butylindenyl)zirconium dichloride,
diethylsilanediylbis(2-methylindenyl)zirconium dibromide,
dimethylsilanediylbis(3-methyl-5-methylcyclopentadienyl)zirconium dichloride,
dimethylsilanediylbis(3-ethyl-5-isopropylcyclopentadienyl)zirconium dichloride,
dimethylsilanediylbis(2-ethylindenyl)zirconium dichloride,
dimethylsilanediylbis(2-methylbenzindenyl)zirconium dichloride
dimethylsilanediylbis(2-ethylbenzindenyl)zirconium dichloride,
methylphenylsilanediylbis(2-ethylbenzindenyl)zirconium dichloride,
methylphenylsilanediylbis(2-methylbenzindenyl)zirconium dichloride,
diphenylsilanediylbis(2-methylbenzindenyl)zirconium dichloride,
diphenylsilanediylbis(2-ethylbenzindenyl)zirconium dichloride and
diphenylsilanediylbis(2-methylindenyl)hafnium dichloride
and the corresponding dimethylzirconium compounds.
Further examples of suitable complex compounds include
dimethylsilanediylbis(2-methyl-4-phenylindenyl)zirconium dichloride,
dimethylsilanediylbis(2-methyl-4-naphthylindenyl)zirconium dichloride,
dimethylsilanediylbis(2-methyl-4-isopropylindenyl)zirconium dichloride and
dimethylsilanediylbis(2-methyl-4,6-diisopropylindenyl)zirconium dichloride and the corresponding dimethylzirconium compounds.
Particularly suitable compounds of the general formula IVd are those in which
M is titanium or zirconium,
X is chlorine, C1-C4-alkyl or phenyl, 
and
R5 to R7 and R9 are each hydrogen, C1-C10-alkyl, C3-C10-cycloalkyl, C6-C15-aryl or Si(R12)3, or two adjacent radicals form a cyclic group of 4 to 12 carbon atoms.
The synthesis of such complex compounds can be carried out by methods known per se, the reaction of the appropriately substituted, cyclic hydrocarbon anions with halides of titanium, zirconium, hafnium, vanadium, niobium or tantalum being preferred.
Examples of appropriate preparation processes are described, inter alia, in J. Organometal. Chem. 369 (1989), 359-370.
It is also possible to use mixtures of different metallocene complexes.
The metallocene-containing catalyst system preferably used for the preparation of the ethylene copolymers b) contains, as component C), a compound forming metallocenium ions.
Suitable compounds forming metallocenium ions are strong, neutral Lewis acids, ionic compounds having Lewis acid cations and ionic compounds having Brxc3x6nsted acids as cations.
Preferred strong, neutral Lewis acids are compounds of the general formula V
M3X1X2X3xe2x80x83xe2x80x83V
where
M3 is an element of main group III of the Periodic Table, in particular B, Al, Ga, preferably B, and
X1, X2 and X3 are each hydrogen, C1-C10-alkyl, C6-C15-aryl, alkylaryl, aryl-alkyl, haloalkyl or haloaryl, each having 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical, or fluorine, chlorine, bromine or iodine, in particular haloaryl, preferably pentafluorophenyl.
Particularly preferred compounds are those of the general formula V where X1, X2 and X3 are identical, preferably tris(pentafluorophenyl)borane.
Suitable ionic compounds having Lewis acid cations are compounds of the general formula VI
[(Ya+)Q1Q2 . . . Qz]d+xe2x80x83xe2x80x83VI
where
Y is an element of main groups I to VI or of subgroups I to VIII of the Periodic Table,
Q1 to Qz are radicals having a single negative charge, such as C1-C28-alkyl, C6-C15-aryl, alkylaryl, arylalkyl, haloalkyl, haloaryl, each having 6 to 20 carbon atoms in the aryl radical and 1 to 28 carbon atoms in the alkyl radical, C3-C10-cycloalkyl which may be substituted by C1-C10-alkyl, or halogen, C1-C28-alkoxy, C6-C15-aryloxy, silyl or mercaptyl,
a is an integer from 1 to 6,
z is an integer from 0 to 5, and
d corresponds to the difference axe2x88x92z, but d is greater than or equal to 1.
Carbonium cations, oxonium cations and sulfonium cations as well as cationic transition metal complexes are particularly suitable. Particular examples are the triphenylmethyl cation, the silver cation and the 1,1xe2x80x2-dimethylferrocenyl cation. They preferably have noncoordinating opposite ions, in particular boron compounds, as also mentioned in WO 91/09882, preferably tetrakis(pentafluorophenyl)borate.
Ionic compounds having Brxc3x6nsted acids as cations and preferably also noncoordinating opposite ions are mentioned in WO 91/09882, a preferred cation being N,N-dimethylanilinium.
The amount of compounds forming metallocenium ions is preferably from 0.1 to 10 equivalents, based on the metallocene complex IV.
Particularly suitable compounds C) forming metallocenium ions are open-chain or cyclic alumoxane compounds of the general formula II or III 
where R4 is C1-C4-alkyl, preferably methyl or ethyl, and m is an integer from 5 to 30, preferably from 10 to 25.
The preparation of these oligomeric alumoxane compounds is usually carried out by reacting a solution of a trialkylaluminum with water and is described, inter alia, in EP-A 284 708 and U.S. Pat. No. 4,794,096.
As a rule, the oligomeric alumoxane compounds obtained in this way are present as mixtures of both linear and cyclic chain molecules of different lengths, so that m is to be regarded as an average value. The alumoxane compounds may also be present as a mixture with other metal alkyls, preferably with alkylaluminums.
Preferably, both the metallocene complexes (component B) and the compounds forming metallocenium ions (component C) are used in solution, aromatic hydrocarbons of 6 to 20 carbon atoms, in particular xylenes and toluene, being particularly preferred.
Aryloxyalumoxanes, as described in U.S. Pat. No. 5,391,793, aminoalumoxanes, as described in U.S. Pat. No. 5,371,260, aminoalumoxane hydrochlorides, as described in EP-A 633 264, silyloxyalumoxanes, as described in EP-A 621 279, or mixtures thereof may furthermore be used as component C).
It has proven advantageous to use the metallocene complexes and the oligomeric alumoxane compound in amounts such that the atomic ratio of aluminum from the oligomeric alumoxane compound to the transition metal from the metallocene complexes is from 10:1 to 106:1, in particular from 10:1 to 104:1.
The metallocene-containing catalyst system preferably used for the preparation of the ethylene copolymers b) may also contain, as component D), a metal compound of the general formula I
M1(R1)r(R2)s(R3)txe2x80x83xe2x80x83I
where
M1 is an alkali metal, an alkaline earth metal or a metal of main group III of the Periodic Table, ie. boron, aluminum, gallium, indium or thallium,
R1 is hydrogen, C1-C10-alkyl, C6-C15-aryl, alkylaryl or arylalkyl, each having 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical,
R2 and R3 are each hydrogen, halogen, C1-C10-alkyl, C6-C15-aryl, alkylaryl, arylalkyl or alkoxy, each having 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical,
r is an integer from 1 to 3
and
s and t are integers from 0 to 2, the sum r+s+t corresponding to the valency of M1.
Preferred metal compounds of the general formula I are those in which
M1 is lithium, magnesium or aluminum and
R1 to R3 are each C1-C10-alkyl.
Particularly preferred metal compounds of the formula I are n-butyllithium, n-butyl-n-octylmagnesium, n-butyl-n-heptylmagnesium, tri-n-hexylaluminum, triisobutylaluminum, triethylaluminum and trimethylaluminum.
If the component D) is used, it is preferably present in the catalyst system in an amount of from 800:1 to 1:1, in particular from 500:1 to 50:1 (molar ratio of M1 from I to transition metal M from IV).
The components B) and C) and, if required, A) and D) are used together as a metallocene-containing catalyst system for the preparation of the ethylene copolymers b) to be used according to the invention.
In addition to the propylene homopolymer a) and the ethylene copolymer b), the novel propylene polymers also contain, if required, a nucleating agent c) which, by definition, accelerates nucleation during crystallization from the melt. The nucleating agents used are those conventionally employed in plastics technology, for example mineral additives, such as talc, silica or kaolin, or organic compounds, such as mono- and polycarboxylic acids and salts thereof, or polymers such as ethylene acrylate copolymers.
Nucleating agents c) which may be present in the novel propylene polymers may be, inter alia, dibenzylidene sorbitol and its C1-C8-alkyl-substituted derivatives, for example methyldibenzylidene sorbitol or dimethyldibenzylidene sorbitol, as well as salts of diesters of phosphoric acid, for example sodium 2,2xe2x80x2-methylenebis(4,6-di-tert-butylphenyl)phosphate.
A particularly preferably used nucleating agent c) in the novel propylene polymer is finely divided talc. The finely divided talc should preferably have a mean particle size of less than 5 xcexcm, in particular less than 3 xcexcm.
The nucleating agents c) described above are conventional commercially available additives. In addition to the nucleating agents c), conventional stabilizers, for example calcium stearate, and phenolic antioxidants, heat stabilizers, UV stabilizers and processing assistants may be added to the novel propylene polymer.
If nucleating agents c) are present in the novel propylene polymers, the propylene homopolymer a), the ethylene-copolymer b) and the nucleating agent c) are usually used in ratios such that from 0.05 to 1.5, in particular from 0.05 to 1.0, particularly preferably from 0.1 to 0.5, parts by weight of nucleating agent b) are employed per 100 parts by weight of the propylene copolymer a) and of the ethylene copolymer b).
The novel propylene polymers are prepared by mixing the nucleating agent c), which may be used, and the ethylene copolymer b) with the propylene homopolymer a) in one of the apparatuses usually used in plastics processing for mixing substances, for example in a drum mixer, a mill, a screw extruder, a disk extruder, a roll mill or a kneader. The propylene homopolymer a), the ethylene copolymer b) and, if required, the nucleating agent c) are mixed with one another in the mixing apparatus usually at from 200 to 250xc2x0 C., in particular from 210 to 240xc2x0 C. The mixing process is carried out as a rule at from 1 to 100 bar and with an average residence time of from 0.5 to 60 minutes. The exact values for the pressure and the average residence time are dependent on the mixing apparatuses used in each case.
Furthermore, the nucleating agent c) may also be sprayed onto the propylene homopolymer a) and onto the ethylene copolymer b).
The novel propylene polymers are distinguished, inter alia, by very high rigidity and flowability in combination with good impact strength. They are moreover readily processable and have only very little tendency to white fracture. Owing to the low tendency to white fracture, the novel propylene polymers are also particularly suitable for utility articles where the appearance plays a role. They can also be used generally as films, fibers and moldings.